A bungarotoxin polypeptide different from Alpha- and Beta-bungarotoxin was purified from bungarus multicintus venom. This peptide termed P-4 bungarotoxin contains 121 amino acids and blocks competitively nicotinic receptor function of adrenal chromaffin cells. Since there are no good nicotinic receptor ligands available to study nicotinic receptors in synaptic ganglia and CNS, P-4 bungarotoxin may represent an useful tool for these studies.